Ce) ee et Vol 66 Tapce II: ® @® @ AprproxrmatTB ARZAS ENCOMPASSED BY gHE EFFECTIVE Briococical Isopose Lines SHOWN IN Tie Map (Fic. 1). Msodose Liue (r) & 109 < 409 *, A erearin tr He Bere ie Pte roe op Smepene * Approxiniate Arees Excompessed (square miles) : 25 ,CO0 12,509 5,099 doses may be extrapolated linearly to any other dose rate at time of failout. For exainple, if fallout begins three hours aiter detonation and the dose rate at that time is 10 r per hour, about 67 r (effective biological dose) will be accumulated provided personnel continues to live normally in the contaminated area. 10 _ 0.15 67 e we ate 0 as? SIATLTS eee Fig. 1. Idealized fallout diagram, based on high- yield nuclear detonation of March +, 1954. Isocdose lines represent efiective biological doses (roentgens). continued occupancy of these areas with no special protective measures. These percentages would, of course, rise within the encompassed areas. The 50-r effec- tive biological isodose line has no unique significance but suggests the magnitude of Itis frankly recognized that in any single dose which might call for emeryency meascurve, such as that shown in Graph 3, there ures against radiation exposures even in the ere inherent a number of uncertainties face of other possible hazards. Tabie II .that are open to discussion. Criteria shows the approximate areas encompassed _ based ondeliberate analyses of the relevant by the three isodose lines. For areas data, however, may be more valid than where the fallout oceurs a few hours or those determined under the duress of an more following detozation, many days or emergency situation. Such a simplified weeks will be required to accuinulate the graph might provide radiological monitors major portion of effective biological doses, with a quick, even if rough, estimate of the so that spot decisions involving additional potential hazards and thusassist in making hazards might not be necessary. decisions as to possible evacuation, etc. FALLOUT PATTERN FROM HIGH-YIELD WEAPONS From Graph 5 and data from other sources (10, 11), an idealized diagram of effective biological doses for fallout from the March }, 1954, surface detonation at the e ihe, Pacific Proving Ground has been prepared (Fig. 1). It is to be emphasized that (a) different yields of weapons, different wind Structures, and different kinds of land surface, would result in different patterns, and that (b) this ts the amount of fallout from a single high-yield weapon. The two innermost isodose lines shown were selected to suggest regions where (a) a significant percentage of personnel might ‘be expected to die (400 r) and (6) a few per cent to becomeill (100 r), assuming PROTECTIVE MEASURES The idealized fallout diagram is based on the assumption that people continue to live normally in an area and that they do nothing special to protect themselves. Actually many measures can be taken to reduce the gamma radiation dose. These may be classified under four headings: 1. Evacuation. 2. Useofshielding. 3. Decontamination of the environs. 4. Al- lowing for lapses of time before entry into a contaminated area. These measures will be discussed onlybriefly. Whererelatively small numbers of people are involved, evacuation could be an easy solution. For large communities, maior factors of danger and/or hardship must be considered. Each situation may be unique, and independent decisions must be